What are Body Composition Tests?

Updated:Aug 26,2016

What is body composition, and why is it important?

Your body is made up of water, fat, protein, carbohydrate and various vitamins and minerals. If you have too much fat — especially if a lot of it is at your waist — you're at higher risk for such health problems
as high blood pressure, high blood cholesterol and diabetes (di"ah-BE'teez or di"ah-BE'tis). That increases your risk for heart disease and stroke.

Obesity is now recognized as a major, independent risk factor for heart disease. If you're overweight or obese, you can reduce your risk for heart disease by successfully losing weight and keeping it off.

Waist circumference and body mass index (BMI) are indirect ways to assess your body composition. Waist-to-hip ratio (WHR) is another index of body fat distribution. However, WHR is less accurate than BMI or waist circumference and is no longer recommended.

What is the waist circumference?

Waist circumference is the distance around your natural waist (just above the navel). If your BMI is greater than or equal to 25 kg/m2, your goal for waist circumference is less than 40 inches if you're a man and less than 35 inches if you're
a woman.

What is the body mass index (BMI)?

Body mass index assesses your body weight relative to height. It's a useful, indirect measure of body composition because it correlates highly with body fat in most people. Weight in kilograms is divided by height in meters squared (kg/m2). In studies
by the National Center for Health Statistics,

BMI values less than 18.5 are considered underweight.

BMI values from 18.5 to 24.9 are healthy.

Overweight is defined as a body mass index of 25.0 to less than 30.0. A BMI of about 25 kg/m2 corresponds to about 10 percent over ideal body weight. People with BMIs in this range have an increased risk of heart and blood vessel disease.

Obesity is defined as a BMI of 30.0 or greater (based on NIH guidelines) — about 30 pounds or more overweight. People with BMIs of 30 or more are at higher risk of cardiovascular disease.

Extreme obesity is defined as a BMI of 40 or greater.

Some well-trained people with dense muscle mass may have a high BMI score but very little body fat. For them, the waist circumference, the skinfold thickness or more direct methods of measuring body fat may be more useful measures.

How do you find your BMI risk level?

Use a weight scale on a hard, flat, uncarpeted surface. Wear very little clothing and no shoes.

Weigh yourself to the nearest pound.

With your eyes facing forward and your heels together, stand very straight against a wall. Your buttocks, shoulders and the back of your head should be touching the wall.

Mark your height at the highest point of your head. Then measure your height in feet and inches to the nearest 1/4 inch. Also figure your height in inches only.

Find your height in feet and inches in the first column of the Body Mass Index Risk Levels table. The ranges of weight that correspond to minimal risk, moderate risk (overweight) and high risk (obese) are shown in the three columns for each height.

Height

Minimal risk
(BMI under 25)

Moderate risk
(BMI 25–29.9)
Overweight

High risk
(BMI 30 and above)
Obese

4'10"

118 lbs. or less

119–142 lbs.

143 lbs. or more

4'11"

123 or less

124–147

148 or more

5'0

127 or less

128–152

153 or more

5'1"

131 or less

132–157

158 or more

5'2'

135 or less

136–163

164 or more

5'3"

140 or less

141–168

169 or more

5'4"

144 or less

145–173

174 or more

5'5"

149 or less

150–179

180 or more

5'6"

154 or less

155–185

186 or more

5'7"

158 or less

159–190

191 or more

5'8"

163 or less

164–196

197 or more

5'9"

168 or less

169–202

203 or more

5'10"

173 or less

174–208

209 or more

5'11"

178 or less

179–214

215 or more

6'0"

183 or less

184–220

221 or more

6'1"

188 or less

189–226

227 or more

6'2"

193 or less

194–232

233 or more

6'3"

199 or less

200–239

240 or more

6'4"

204 or less

205–245

246 or more

To calculate your exact BMI value, multiply your weight in pounds by 703, divide by your height in inches, then divide again by your height in inches. (Adapted from Obesity Education Initiative: Clinical Guidelines on the Identification,
Evaluation, and Treatment of Overweight and Obesity in Adults, National Institutes of Health, National Heart, Lung, and Blood Institute, Obesity Research 1998, 6 Suppl 2:51S-209S)